How is clay made of

Clay (soil type)

volume refers to a naturally occurring material that is mainly composed of fine-grained minerals and can contain variable amounts of water. With the appropriate water content, clay is plastic, i.e. malleable. Clay hardens when it is dried or fired.

The clay minerals that give clay its plastic properties are generally layered silicate. In addition, clays can contain other organic and inorganic materials that do not contribute to the plastic properties, such as B. quartz, calcite, dolomite, feldspars, oxides, hydroxides or also colloidal silica, iron hydroxide gels or organic gels. The clays do not include artificially produced materials with clay properties or materials with predominantly organic components, even if these have the plastic properties of clay and are of natural origin.[1]

This definition of the AIPEA (Association Internationale Pour L’Etudes Des Argiles) does not specify the exact grain size of the clay components, as various disciplines have made their own specifications here. In geology and soil science, in accordance with the EN ISO 14688 standard, clay particles are particles with sizes <2 µm, in sedimentology <4 µm, in colloid chemistry <1 µm.


Pottery and ceramics

The use of clay as a raw material for pottery and ceramics is documented well into the Upper Paleolithic. Already around 24,000 years BC Mammoth hunters made clay figures such as the Venus of Dolní Věstonice, which was found in the Czech Republic along with numerous animal figures.

Building material

Clay is one of the main components of clay and has been used as a building material for around 10,000 years in the form of air-dried clay bricks and clay plaster. Between 3100 and 2900 BC Baked clay in brick shape was used for the first time on a large scale. Since then, at the latest, clay has been one of the most important building materials of mankind. At the beginning of the new millennium, the clay component was further developed into a new type of plaster.

In addition, sound z. B. required for the sealing layer of dykes and the sealing of landfills against the subsoil. Mighty formations of high-density clay are being discussed as repositories for radioactive waste.

Clay has been used as a raw material for cement production since the 20th century.


Clay is an important raw material for the production of chamottes, which are used for the interior lining of stoves, for example. B. are required in the steel and glass industry.

In the manufacture of paper, clay is used as a filler to make the paper softer and more pliable and to give it a smooth surface.


Clays of various compositions have been used for therapeutic purposes since prehistoric times. The mechanisms of action are often poorly understood in detail. First and foremost, the high adsorption capacity of the very fine-grain layered silicates is cited as an explanation for the observed healing effects. On the one hand, nutrients bound to the mineral surfaces can be released; on the other hand, toxins can be bound to the clay minerals and thus neutralized.

Current studies show that some deposits of iron-rich clays have a bactericidal effect. [2] The clay minerals themselves (Fe smectite, 1MdIllit) are less effective here than the high pH value (> 9) of the clay suspensions in combination with dissolved trace elements (Na, Mn, As, Ag, Mo, U). [3]


  • S. Guggenheim et al. 2006: Summary of Recomandations of Nomenclature Committees Relevant to Clay Mineralogy: Report of the Association Internationale Pour L’Etudes Des Argiles (AIPEA) Nomenclature Committee for 2006, Clays and Clay Minerals, Vol. 54, No. 6, 761-772
  • S. Guggenheim 1995: Definition of Clay and Clay Mineral: Joint Report of the AIPEA Nomenclature and CMS Nomenclature Committees, Clays and Clay Minerals, Vol. 43, No. 2, 255-256
  • Hillier S. (2003) Clay Mineralogy. pp 139-142 In: Middleton G.V., Church M.J., Coniglio M., Hardie L.A. and Longstaffe F.J. (Editors) Encyclopedia of sediments and sedimentary rocks. Kluwer Academic Publishers, Dordrecht.
  • Lynda B. Williams et al. 2008: Chemical and Mineralogical Characteristics of French Green Clays Used for Healing, Clays and Clay Minerals, Vol 56, No. 4, 437-452 manuscript

Individual evidence

  1. ↑ Guggenheim et al. 1995: Definition of Clay and Clay Mineral
  2. ↑ Broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens
  3. ^ Chemical and Mineralogical Characteristics of French Green Clays Used for Healing

Web links

 Commons: tone - Collection of pictures, videos and audio files
Template: Commonscat / WikiData / Difference